
• When magma reaches the surface it loses its gases and
become lava
• The igneous rocks that form on the surface are called
extrusive or volcanic (after the fire god Vulcan).
• Magmas that fail to reach the surface crystallize below
the surface and produce the intrusive or plutonic rocks
(after Pluto, the god of the lower world).
• Plutonic rock would only appear on the surface of the
Earth when crust is uplifted and the overlying rocks are
eroded. The exposures of these rocks are called outcrops
Igneous Rocks